Daily Mail Tuesday, April
15th 2003
Warning: Soya May Be Making Men Infertile
By James Chapman, Science Correspondent
The increasing amount of soya being eaten in Britain could be
putting the
fertility of a generation of men at risk, according to an alarming
new study.
Researchers believe that pregnant or breast-feeding women who
eat soya and
soya-based products, such as tofu, could be endangering their
babies because
these foods contain chemicals that mimic the female hormone,
oestrogen.
Experts fear that exposure in the womb, or through breast milk,
could lead to
reproductive abnormalities in boys. They are also concerned
about the
possible impact of soya-based infant foods.
The scientists, based at Johns Hopkins University in Baltimore,
Maryland,
tested the effects of genistein - the key chemical found in
soya beans - on
pregnant rats. Alarmingly, they found that their male offspring
developed
abnormal reproductive organs and experienced sexual dysfunction
as adults.
The researchers are calling for more research to be carried out
urgently to see
if the increasingly popular soya and soya-based foods affect
human
reproductive development in the same way. The warning is supported
by the
Scientific Advisory Committee On Nutrition, which advises the
British
Government. It said last month there is "clear evidence" that
soya-based
formula milk could damage children's sexual development and
fertility as
adults. Large amounts of genistein are found in some baby formula
milks and
supplements taken by women, as an alternative to hormone replacement
therapy.
The average sperm count of a European male has dropped by a quarter
over
the past 25 years and about 27,000 British couples seek treatment
for
infertility problems each year, an increase of 55 per cent in
five years. As many
as one in six couples is thought to have problems conceiving.
In the new study, published in the latest issue of the Journal
Of Urology,
pregnant female rats were randomly assigned a genistein-free
diet or one
containing the chemical. Male offspring were exposed to genistein
indirectly
through maternal consumption during pregnancy and after birth
through
breast milk. When the offspring who were exposed to genistein
matured,
researchers found the males had smaller testes and a larger
prostate gland and
lower testosterone levels compared to unexposed rats. Although
their sperm
counts were normal, exposed adult males had lower testosterone
levels and
were also less likely to mate successfully.
"The effects of genistein continued long after the rats were
exposed", said Dr
Amy Wisniewski, who led the research at the Johns Hopkins Childrens
Centre. "This leads us to believe that exposure to this plant-derived
oestrogen
during reproductive development can have long-term detrimental
effects in
males".
Dr Sabra Klein, another member of the research team, added: "Genistein
may
act as an oestrogen or an anti-androgen, blocking the function
of endogenous
androgens - the sex hormones necessary for males to develop
a normal
reproductive system".
"Ultimately, it appears this leads to the reproductive abnormalities
and sexual
dysfunction we saw in the exposed rats. However, additional
research is
needed to determine if this is the case".
Whether the long-term effects of genistein on reproductive development
are
caused by exposure during gestation, lactation or both also
requires further
investigation, the scientists said.
Daily Mail Tuesday, April 15th 2003
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